<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    let num1 = +prompt('请输入第一个数字')
    let num2 = +prompt('请输入第二个数字')
    let sq = prompt('请输入运算符')
    switch (sq) {
      case '+':
        alert(`${num1 + num2}`)
        break;
      case '-':
        alert(`${num1 - num2}`)
        break;
      case '*':
        alert(`${num1 * num2}`)
        break;
      case '/':
        alert(`${num1 / num2}`)
        break;
      default:
        alert('请输入正确的格式')
        break;
    }
  </script>
</body>

</html>